1. Field of the Invention
The present invention relates to a novel enzymatic method to produce xylose and a method of detecting xylose in vitro.
2. Background Art
Xylose is a pentose sugar. D-xylose is the form found primarily in plants and animals. Xylose is recognized as being useful as an additive; as a food; as a pre-cursor for xylitol; as a sweetener; as a glucose substitute for diabetic patients (xylose does not provoke insulin response like glucose); as a therapeutic for decreasing transaminase and ketone levels in hepatitis patients, for connective tissue disorders and for osteoarthritis; and for industrial uses, such as dyeing, tanning, furfural production, paint, acetic acid production, lactic acid production, biodegradeable plastic polymer production, glue, resins, vitamin C production, and ethanol fuel production.
Xylose is a major component of hemicellulose. Hemicellulose is a component of lignocellulose, which is found in plants, for example, forage plants, woody plants, bark, beechwood, corn husks, oat hulls, canes, coffee grounds, straw, and bulk plant products. Xylose can be recovered from agricultural waste and hardwood in good yield by acid hydrolysis, using acetic acid or sulfuric acid. However, acid hydrolysis of hemicellulose results in the presence of varying amounts of many hexoses and pentoses, including arabinose, galactose, mannose, rhamnose, and glucose, in the same preparation as the xylose.
Acid hydrolysis of lignocellulose, however, liberates different sugars, such as a mixture of D- and L-sugars, as well as furfurals, acetic acid, hydroxybenzoic acid and vanillin, among others. Therefore, processing xylose from bulk plant products or from sources of hemicellulose or lignocellulose suffers from the disadvantage of the presence of many products from the acid hydrolysis, making the extraction of xylose from the by-products costly. Some of these side products, in particular the furfurals, inhibit the growth of microorganisms. Therefore, one disadvantage of using sources of hemicellulose and lignocellulose for the production of xylose is that many of the products produced by acid hydrolysis of hemicellulose and lignocellulose inhibit microbial metabolism and subsequent utilization of the sugars (Ooi et al., Electron. J Envrion. Agric. Food Chem. 1(3), (2002)). Because of the numerous side products, additional purification of the xylose product is required.
Therefore, there exists a need for improved methods of producing xylose, which produces fewer by-products.